Toxic cyanobacterial breakthrough and accumulation in a drinking water plant: a monitoring and treatment challenge.
ABSTRACT The detection of cyanobacteria and their associated toxins has intensified in recent years in both drinking water sources and the raw water of drinking water treatment plants (DWTPs). The objectives of this study were to: 1) estimate the breakthrough and accumulation of toxic cyanobacteria in water, scums and sludge inside a DWTP, and 2) to determine whether chlorination can be an efficient barrier to the prevention of cyanotoxin breakthrough in drinking water. In a full scale DWTP, the fate of cyanobacteria and their associated toxins was studied after the addition of coagulant and powdered activated carbon, post clarification, within the clarifier sludge bed, after filtration and final chlorination. Elevated cyanobacterial cell numbers (4.7 × 10(6)cells/mL) and total microcystins concentrations (up to 10 mg/L) accumulated in the clarifiers of the treatment plant. Breakthrough of cells and toxins in filtered water was observed. Also, a total microcystins concentration of 2.47 μg/L was measured in chlorinated drinking water. Cyanobacterial cells and toxins from environmental bloom samples were more resistant to chlorination than results obtained using laboratory cultured cells and dissolved standard toxins.
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ABSTRACT: Cyanobacteria in water treatment sludge pose a health risk as they continue to be viable, multiply, and produce potentially harmful secondary metabolites. To date, little research has focused on accurately determining cell bound microcystin (MC) concentrations of cyanobacterial cells in water treatment sludge. Three extraction methods (freeze-thaw, lyophilisation, direct methanolic extraction) with three different pre-treatments (homogenisation, (ultra)sonication, combination of both, and controls) were investigated for their MC extraction recovery. It was found that lyophilisation with prior sonication achieved the highest toxin recovery across the two MC analogues (MC-LR, MC-LA) tested. The method was able to extract 69 and 56% of MC-LR and MC-LA, respectively with good reproducibility. Comparable results were also obtained with direct methanolic extraction, with poor reproducibility. The least efficient method was freeze-thawing which achieved poor recoveries and was less reproducible. This study highlights a rapid, efficient, low-cost extraction method for determining total microcystins in cyanobacterial-laden sludge.Journal of Chromatography B. 01/2014;
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ABSTRACT: The intermediates and byproducts formed during the ozonation of microcystin-LR (MC-LR, m/z = 995.5) and the probable degradation pathway were investigated at different initial molar ratios of ozone to MC-LR ([O3]0/[MC-LR]0). Seven reaction intermediates with m/z ≥ 795.4 were observed by LC/MS, and four of them (m/z = 815.4, 827.3, 853.3 and 855.3) have not been previously reported. Meanwhile, six aldehyde-based byproducts with molecular weights of 30-160 were detected for the first time. Intermediates structures demonstrated that ozone reacted with two sites of MC-LR: the diene bonds in the Adda side chain and the Mdha amino acid in the cyclic structure. The fragment from the Adda side chain oxidative cleavage could be further oxidized to an aldehyde with a molecular weight of 160 at low [O3]0/[MC-LR]0. Meanwhile, the polypeptide structure of MC-LR was difficult to be further oxidized, unless [O3]0/[MC-LR]0 > 10. After further oxidation of the intermediates, five other aldehyde-based byproducts were detected by GC/MS: formaldehyde, acetaldehyde, isovaleraldehyde, glyoxal and methylglyoxal. Formaldehyde, isovaleraldehyde and methylglyoxal were the dominant species. The yields of the aldehydes varied greatly, depending on the value of [O3]0/[MC-LR]0.Water research. 06/2014; 63C:52-61.
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ABSTRACT: Probability of a cyanobacteria bloom occurrence at a drinking water treatment plant as a function of a meteorological factor, f(p).Water Research 01/2014; 56:98–108. · 5.32 Impact Factor